1. Field of the Invention
The present invention relates to a detergent composition. In particular, it relates to a detergent composition which contains a water-soluble amino polycarboxylic acid compound excellent in biodegradability and exhibits excellent detergency.
2. Description of Related Art
A detergent for clothes is composed of a surfactant which solubilizes soil, separates it from fibers, and dissolves or disperses it in a water for washing, an alkali agent which accelerates the decomposition or solubilization of soil, a polymeric substance which suspends soil, a sequestering agent which removes substances lowering the power of surfactants, for example, calcium, magnesium and so on from a water for washing, and so on.
Among these components, the substance, called a builder in general, does not exhibit detergency by itself, but can enhance the detergency of a surfactant used together. In the builder for a detergent, the above-mentioned sequestering agent serves to make a surfactant exhibit its performance more effectively, thus being one of extremely important builders.
Phosphorus compounds such as sodium tripolyphosphate were formerly added to a detergent for clothes as the builder (i.e., sequestering agent). However, phosphorus compounds were believed to be one of the factors causing the eutrophication of rivers, lakes, ponds and so on. In the detergent industry, therefore, the use of phosphate builders was self-restrained, while the development of a detergent without any phosphate builder had been continued. As a result, a zeolite, a crystalline sodium aluminosilicate, having a specific structure was used as the main component of the sequestering agent.
Although the zeolite was used as the main builder substitute for phosphorus compounds, it had some problems that the performance thereof in low-temperature washing in a short time was often unsatisfactory and that the degree of freedom of the formulation was restricted in order to decrease the quantity of insolubles derived from zeolite which was essentially insoluble in water.
Owing to the recent high concern about the influence on the environment, studies have been made on organic builders excellent in biodegradability and sequestering performance. There is so this background that, for example, a specific organic builder prepared by the reaction of epoxysuccinic acid or maleic acid with aspartic acid and a detergent composition containing it is disclosed in JP-A 5-170714, and a detergent composition containing a builder consisting of hydroxyiminodisuccinic acid in a specific amount is disclosed in JP-A 6-248300.
Further, it is suggested in JP-A 50-3979 and JP-A 56-81399 that an N,N-bis(carboxymethyl)glutamic acid salt is superior to the above organic builders in calcium sequestering performance and biodegradability, and such a salt is usable as builders for a detergent. However, these patent documents are silent on the detergent composition which enable the builders to exhibit their effects sufficiently.